Jack mechanism having an internal locking means



F. S. PEARNE June 25, 1963 JACK MECHANISM HAVING AN INTERNAL LOCKING MEANS 4 Sheets-Sheet 1 Filed Dem 29, 1959 INVENTOR Frank SPearne ,L BY i?,

ATTORNEYS June 25, 1963 F. s. PEARNE 3,094,841

JACK MECHANISM HAVING AN INTERNAL LOCKING MEANS Filed Dec. 29, 1959 4 Sheets-Sheet 2 INVENTOR Frank S- earne BY l ATTORNEYS June 25, 1963 JCK MECHANISM HAVING AN INTERNAL LOCKING MEANS Filed Deo. 29, 1959 F. S. PEARNE 4 Sheets-Sheet 5 Z5 INVENToR Frank Pearne Lu/WIL ATTORNEYS United States Patent O California Filed Dec. 29, 1959, Ser. No. 862,648

This invention relates to a jack mechanism having an internal locking means, and, more particularly, to an improved hydraulic jack structure having an extensible ram land an internal locking means for releasably locking the ram in `an extended position.

The invention is particularly concerned with hydraulic jacks which vare required to be repeatedly and quickly extended to support a load, locked in the extended position, and then unlocked and retracted. In order to satisfy these requirements, I have devised unique internal locking means for the ram which can be manipulated in a facile manner to quickly lock the ram `so that it may support a load, land then to unlock the ram in an equally easy fashion whereby the ram can be retracted. My novel jack mechanism =also includes means to automatically retract the ram when the ram has been unlocked. For illustrative purposes, the invention has been shown and described in conjunction with both a leveling jack and an aircraft tripod jack, however, it is to be understood that the invention may be embodied in many other types of jacks.

`Conventional jack constructions commonly employ a locknut which is threaded on the extended portion of the ram into abutment `or engagement with the outer shell of the jack to hold the ram in its extended position. This type of construction possesses -several disadvantages, the most significant of which is the relatively long time which is required to lock and unlock the ram. Another disadvantage is that, when a jack employing this form of locking means is used out-of-doors, water frequently runs down the threads of the locknut and enters the cylinder thereby seriously affecting the operation of the jack.

With specific regard to the construction of leveling jacks such as are used on load-supporting vehicles to level the vehicle and to raise the load from the wheels when the vehicle is stationary, the forms of constructions heretofore known possess additional disadvantages over and above the ram locking means.` One major objection in the case of leveling jacks permanently mounted on a vehicle is that, commonly, no means are provided for automatically retracting the ram when it is unlocked. As a result, the ram is often left at least partially extended through inadvertence of the operator when the vehicle is moved, and, hence, the ram is frequently damaged when the vehicle passes over a slight ground rise or the like. Another disadvantage is that the fluid supply or reservoir for the jacks is often separate from the main body or shell thereby making the entire assembly extremely unwieldy and difficult to install in the available space. s

An object of the present invention is to provide a jack mechanism with internal ram locking means which may be operated in a facile manner to lock the ram in an extended position and then to quickly unlock the ram when the latter element is to be retracted.

Another object is to provide a jack mechanism having internal ram locking means of the type `described with means for automatically retracting the unlocked ram.`

Still another object is to provide ya jack mechanism with Yinternal ram locking means whereby water encountered in outdoor use is prevented from entering the cylinder of the jack.

Another more speciic object of the invention is to pro- 4 within the shell.

vide a unique hydraulic leveling jack mechanism having internal ram locking means and a self-contained uid reservoir.

Other objects and advantages of the invention will become more readily apparent when the same is considered in connection with the following detailed description and the accompanying drawings wherein: Y

FIGURE l is a schematic side elevation of a dolly having attached leveling jacks constructed in accordance with my invention.

FIGURE 2 is a side view of my novel leveling jack construction.

FIGURE 3 is a vertical section of the leveling jack shown in FIG. 2 showing one embodiment of the internal ram locking means.

FIGURE 4 is a view similar to FIG. 3 but showing the ram in an extended and locked position.

FIGURE 5 is a horizontal sectional view taken through the jack near the top thereof along the line 5--5 of FIG. 3.

FIGURE 6 is an enlarged vertical sectional view of a portion of the jack showing the piston in an upstroke and showing a uid by-pass opening for retracting the jack.

FIGURE 7 is a side eleva-tional view of a portion of the internal locking means for the ram.

FIGURE 8 is a fragmentary side elevational view showing another portion of the internal locking means.

FIGURE 9 is a fragmentary side elevation showing the assembled locking mechanism.

FIGURE l0 is a fragmentary side elevation, partly in section, of a leveling jack having a modified locking mechrand l1.

FIGURE 13 is shown in FIG. 12.

FIGURE 14 is a horizontal sectional View taken through the jack of FIG. 12 near the top thereof along the line 14-14 of FIG. 13.

Referring now to the drawings, the apparatus embodying my invention may be in the form of a leveling jack which is used to stabilize and level a load relative to the ground Ior other supporting surface. As shown diagrammatically in FIG. l, four such jacks 20 may be arranged at the corners lof a missile dolly D adjacent each wheel. When the dolly is being moved, the jacks are maintained above the lower wheel surfaces, and when the dolly is stationary, as in a tiring position or a storage position, the jacks are lowered or extended to raise the weight of the loaded dolly from the wheels. As will hereinafter be discussed in more detail, the construction of the jacks is such that they are automatically fully retracted from their extended, load-bearing position, thereby eliminating the hazard of the jacks being inadvertently left in a partially extended position and damaged when the dolly is moved over a slight ground rise. My novel leveling jack is not limited, of course, to use on vehicles since it is equally ywell adapted to be used in conjunction with any support equipment.

Referring next to FIGS. 2 through 9, there is shown in detail aleveling jack construction embodying one form of my invention. The principal components of the illustrated pack include an outer shell 21 having a load carrying ring 22 welded or otherwise secured thereto, a ram 23, a main shaft 24, a pump cylinder 25, and a piston 26, the latter four components being concentrically nested A foot pad 2-7 is connected to the ram and is adapted to be pushed by the foot of the operator a vertical sectional view of the jack Ajoined to 'D a 4into initial contact with the ground, as shown in dot-dash outline in FIG. 2, while a handle 2S, operatively connected to the piston 26, is adapted to ,be actuated `by the hand-of the operator -to apply hydraulic pressure to the Vextended ram.

The outer shell 21 preferably is in the form of an open-ended cylinder, and includes a collar 33 permanently secured to the inner surface of the end. The collar includes `an inner groove 34 which receives an O-ring 35, while the inner Surface of the upper end of the shell is notched to receive a locking ring 36. The Iload ring 22 may be fastened to the outer periphery of the Shell 21 `approximately onethird of the distance from the bottom toward the t-op of the shell.

The -ram 23 is also in the form of a hollow cylinder, and has a diameter such which has a threaded recess 42 in its bottom, and the foot pad 2'7 vthe bottom and top,

shaft. The diameter of the shaft base 50 is equal to that head. The outer shell 21, shaft head 45 and shaft :base 50 define a fluid reservoir 49vfrom which uid is drawn during operation of the jack.

In order lthat the vided with an internal ram locking means or ratchet includes sloped ratchet teeth As shown most clearly in FIGS. 4 and 5, each dog plate or arm is substantially the same width as the shaft, and is rotatably mounted on a lock base r58 by curved varms 59 which are received in an aperture 60 in each dog plate.

numeral 64, may Aalso be provided to assist lin fastening the lock plate and rarn together. The 'dog plates are urged into ratcheting engagement with teeth 55 by -a surrounding garter spring 65 which abuts posts 66 located at each side of each dog plate or arm.

In order that the dog plates 56 and 57 can be biased Y out of and away from the i opposed flat sides of the main shaft 24. FIGS. 7, 8 and 9, these straps are shown to depend from a lock release 72 which has a U-shaped bottom portion with bifurcated legs 73 surrounding the main shaft and an attached bar 74 projecting upwardly through the shaft head 49. fThe straps 7) and 71 are provided with flanges 75 at their upper ends, the flanges being received between the `bifurcated legs 73 so that upward and downward will press the Ystrap 70 into engagement with a laterally projecting leg 78 connected to one side of dog plate 5:6, and strap 71 into engagement with a leg 79 connected Vof the dogs 56 and 57, respectively, and disposed on the piston, prevents `iluid from entering chamber through the open lower end of the piston. The outer surface of the :piston is relieved at 107 in the region of chamber 100 to form, in .conjunction with ports 165 and 106 in the-main shaft and cylinder,` respectively, and ports 10S flow path whereby iluid contained Piston 26 is raised and lowered by actuation of the pump handle 28. As indicated in FIGS. 2 Iand 3, the handle 28 is channel shaped and has one connected to an end of link 121, the other end of the link being pivotally connected to a collar 122 surrounding the outer shell 21. The legs 123 -of the channel- Referring to respect to the shell 21 by shaped handle` may be crimped inwardly in an area generally designated by reference numeral 124, and fitted into engagement with a neck 125 on the top end of piston 26. When assembled in the manner illustrated in FIG. 2, the handle may lbe moved laterally with respect to the axis of the piston thereby providing a lever arrangement having a mechanical advantage that can be varied as desired. Also, the collar 122 can be rotated with loosening bolt 126 in order to change the pumping position of the handle. When not in use, the crimped area of the flanges 123 may be disengaged from the piston neck, and the handle thrown over the top of the jack so that it depends vertically along the side of the shell, this position being shown in FIG. 2 in dot-dash outline.

yWhen it is desired to operate the jack, the operator rst pushes down the foot pad 27 until it contacts the ground, thereby drawing the ram 23 downward in the shell 21. As the ram is extended below the shell, there is formed between the ram base 41 and the shaft base 50 the pressure area 67. ,This area is promptly flooded by hydraulic duid which passes through the uid ports 105 and 106 into the cylinder area 107, and then into the feeding chamber 100 through ports 108. Check valves 1'02 and 96 permit liuid in the chamber 100 to ow through passageway 54 into the pressure area. It is possible, of course, to initially extend the ram by reciprocating the piston 26, however, this procedure requires more time than to simply push down on the foot pad.

The ram is automatically locked in the extended position by the dogs or arms 56 and 57 which engage the teeth 55 on the main shaft 24. "This locking engagement is permitted when the lock release 72 is in an up position with the pins 77 in the bottoms of the respec- 'tive cam slots. When in this position, the straps 70 and 71 will be out of contact with the dog yactuating legs 78 'and 79, respectively, allowing the spring 65 to bias the dogs inwardly.

. With the ram extended, the operator then engages the pump handle 28 with the piston 26, and adjusts the handle and the collar 122 to obtain the optimum mechanical -advantage and pumping position. As the handle is oscillated to actuate the piston, fluid between the check valves 102 and 94 will be forced by downward movement of the piston' past the check valve 94 into the pressure area 67 to further extend and pressurize the ram. It will be apparent that, during the upstroke of the piston, the check valve 94 will sea-t to prevent hydraulic fluid from leaving the pressurea-rea 67 and valve 102 will open to lill the space between the valves 94 and 102.

YWhen the ram is to be retracted, the operator first pushes down on the lock release 72. This causesthe straps 70 and 71 to move vertically with respect to the stationary main shaft. As indicated in FIG. 9, the resulting relative movement of pins 77 in the cam groove shifts the straps laterally, whereby strap 70 contacts leg 78 to push 56 away from the teeth 55 on one side of main shaft 24, and strap 71 contacts leg 79 to push dog 57 away from the teeth `on the opposite side of the main shaft.

With the internal locking mechanism thus disengaged, the operator next turns plate 90 to raise the .attached cylinder 25 and valve sea-t 92 away from the shaft base 50 to the position shown in FIG. 6. In this position the check valves 94 and 102 are by-passed and fluid is free to pass from the pressure area 67 into the space between the pump cylinder 25 and main shaft 24, and thence through ports 105. At the same time the ram is -automatically fully retracted under action of spring 40.

As the ram retracts under spring action, the dog plates 56 and 57Ywill come into contact with the lock release 72 and lwill push the release upwardly to the position shown in lFIG. 3. AMovement of the lock release pulls along rthe straps and again causes relative movement of the pins 77 in the cam slots tow-ard the bottom of the slots. This movement shifts strap 70l to the left yand str-ap 71 to the right, as viewed in FIG. 6, whereupon the dogs 56 and 57 are permitted to again engage the teeth preparatory to another operation. The valve se-at 92 may then be moved back into the mouth of passageway 54 by reverse rotation of the plate 90. Alternatively, the by-pass may be kept open until the pressure area is again ooded, and then re-seated. p

There is shown in FIGS. l0 and lil a modified form of my novel leveling jack in which the internal locking mechanism is in the form of a ratcheting, scissors-type gripping means which co-operates with teeth yon the main shaft :to hold the ram in an extended position.

The principal components of the jack shown in FIGS. l0 and vll are essentially the same as described in lconnection with the construction of FIGS. l through 9, there being an outer shell 21, a ram 23, a main shaft 24a, a cylinder 25, and a piston 26. The ram is urged toward a retracted position by a compression spring 40, while the piston is actuated by a pump handle 28.

In this embodiment, however, the main shaft 24a is in the for-m of -a hollow cylinder instead of being a square shaft with a square bore, there being teeth on the periphery of the shaft 24a extending along a major portion of its length.

The internal locking mechanism includes arms 141 and 142 pivotally mounted in a scissors-type arrangement by pivot 143 on a lock base 144, the lock base being integr-ally joined to the top of ram 23. As most clearly shown in FIG. l-l, the arms 141 and y142 encompass the main shaft, and, when closed by springs 145 which are fastened to the free end of each arm, co-operate with circumferential teeth 140 to hold or lock the lram in a fixed position.

The pivotally connected ends of arms 141 and 142 are provided with ears 147 and 146, respectively. A release rod 143 having a release handle 149 on its upper end, is rotatably mounted in the shaft head 45 Iand extends between the ears in a direction parallel to the main shaft, while suitable means (not shown) are provided for rotatably mounting the lower end of the release rod at the bottom of the jack. As shown, the release rod is of square cross-section between the shaft head and the bottom of the jack, however, it may have various other shapes as long as they have unequal radial dimensions for camming the arms 141 and 142 apart against the action of the springs 145 when the release rod is rotated through an angle about its axis.

In operation, the ramis extended by the operator as lin the previously described embodiment, the arms 141 and 142 serving to prevent upward movement of the ram under action of spring 145. When the ram is to be retracted, the operator has only to turn the release handle 149,0n the rod 14S. The twisting of the release rod serves to cam the ears apart and to thereby separate the arms and move them radially out of contact with the teeth 140. Once the arms and teeth are disengaged, the `spring 40 will retract the ram, `at which time the rod may again be turned to its first position so that the arms will re-engage the teeth under the action of spring 145.

The scissors-type internal locking mechanism is particularly suitable to be incorporated into an aircraft tripod jack, and this arrangement is shown in FIGS. l2, 13 and 14. In the illustrated embodiment, reference numeral lsrdesignates the legs of jack, the legs being attached to `their upper ends to a collar 151 which is connected to an outer shell 152 of the lifting mechanism. The bottom of the shell 152 and a hand pump assembly 153 are mounted on a bottom plate 154, which is attached to each leg 1563 as shown.

A ram is reciprocally mounted within the outer shell, and is spaced a short distance inwardly from the 75 inner wall thereof by internal rings 161 and 162. The

ring 161 is secured to lthe inner surface of shell 152, While ring 162 is carried by the ram.

A cylindrical main shaft 164, having an annular shaft head 165 and a shaft base 166, is positioned within the ram and is secured to the ram for movement therewith by means of a locking ring 167 which locks the ange 168 of the shaft head 165 to the upper end of the ram. As indicated in FIG. 13, the ram and main shaft are spaced apart by a ange 168 on the shaft head 165, and this space constitutes a fluid reservoir 169 which may be filled with hydraulic iiuid through the ller plug 171i. The main shaft assembly further includes a screw extension shaft 181 which is received within the main shaft and which is threadedly engaged with the interior bore of the shaft head 165.

through a passageway (not shown) in the bottom plate 154 and is injected by the pump into the pressure zone through a bore 172 in the plate 154 and a port 173 in the pedestal 171.

A sleeve 182 is txedly mounted 169, the bottom viously described embodiment, the scissors arms are biased inwardly by springs 177 attached to the free ends of the arms, while ears 179 and 178 on arms 174 and 175, respectively, co-operate with a release rod 180. The release rod projects downwardly through the bottom plate 154 and has a release handle secured thereto.

The jack may be operatively extended by pumping hydraulic iluid, by means of the hand pump assembly 153, from the reservoir through the bore 172 and port teeth on the main shaft to hold the same in a raised position, thus locking the ram in an shown in dot-dash outline in FIG. 12. sion may also be threaded upwardly to provide increased height if such is desired.

When the ram is to be retracted, the operator twists the release rod 180 to separate Obviously many other modications and variations of the specific forms of the invention herein are possible in the light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically shown and described.

What is claimed is:

l. A jack mechanism comprising an outer shell, a hollow, extensible ram telescopically mounted in one end ponents relatively movable along the longitudinalaxis of said shell, first means connecting a irst one of said comland extending into said fluid reservoir, strap means hanging from said lock release, a diagonal cam slot n said strap means, pin means fastened to said second means and extending through said cam slot whereby vertical movement of said lock release will cause said strap means to move toward and away from said iirst one of said components, a laterally extending leg on said first one of said components, said leg being engageable with said strap means upon movement of said, strap means toward the first one of said components to force the rst one of said components away from said second means thereby unlocking said ram to permit said ram to be moved relative to the shell.

2. A jack mechanism comprising an outer shell, a hollow, extensible ram telescopically mounted in one end of said shell, said shell and said ram defining a substantially said teeth to lock said arm and main shaft against said relative movement, second means for positively moving said surface of the arm out of engagement with said teeth to permit said relative movement, said second means comprising a lock release slidably mounted on said main shaft, strap means hanging from said lock release, a diagonal cam slot in said strap means, pin means fastened to the main shaft and extending through said cam slot whereby vertical movement of said lock release will cause said strap means to move toward and away from said arm, a laterally extending leg on said arm, each leg being engageable with said strap means said ram for retraction, means connecting said main shaft one to said shell and the other having an youter shell and an extensible ram telescopically mounted within said shell, said shell and said ram [defining a substantially closed cause said strap means to move toward and away from said rst component, a laterally .extending leg on said first component, said leg being engagea'ble with said strap means upon movement of said out of locking engagement.

4. A jack mechanism comprisingv an outer shell, an extensible ram telescopically mounted within said shell, a

main shaft fixedly mounted within said shell, said shell, ram, and shaft defining a substantially closed fluid reservoir, pressure means for extending said ram, internal locking means within said reservoir for releasably locking said ram in an extended position, said internal locking means including teeth formed on the peripheral surface of said main shaft, an arm having a teeth engaging surface movably mounted on said ram, means attached to said arm for yieldably moving the teeth engaging surface of the arm into engagement with said teeth, a lock release slidably mounted on said main shaft, strap means hanging from said l'ock release, a diagonal cam slot in said strap means, pin means fastened to the main shaft and extending through said cam slot whereby vertical movement `of said lock release will cause said strap means to move toward and away `from said arm, a laterally extending leg on said arm, each leg being engageable with said strap means when the strap means is moved toward the arm to 4force the arm away from said main shaft thereby unlocking said ram for retraction.

5. A jack mechanism as claimed in claim 4 including spring biasing means operatively connected to said ram and shell for automatically retracting said ram when said teeth engaging surface is out of engagement with said teeth.

6-. A jack mechanism comprising an outer shell, an extensible, hollow ram concentrically mounted within said shell, a main shaft mounted within said ram, said main shaft being fixedly secured to said shell, said shell, ram, and shaft defining a substantially closed fluid reservoir, means defining a pressure chamber within said hollow ram for hydraulically extending said ram, and internal locking means within said reservoir for locking said ram in an extended position, said internal locking means including teeth formed on the peripheral surface of said main shaft, a pair of arms pivotally mounted on said ram, said arms having teeth engaging surfaces located on opposite sides of said shaft, spring means surrounding said arms whereby said teeth engaging surfaces are yieldably unged into co-operative engagement with said teeth, a lock release slidably mounted on said main shaft, a pair `of straps hanging from said lock release adjacent opposite sides of said main shaft, a diagonal cam slot in each strap, the cam slot in one strap being formed criosswise of the cam slot in the other strap, a pair of pins fastened to the main shaft and extending through said cam slots whereby vertical movement of said lock release 4will cause said straps to move toward and way from said arms, a laterally extending leg on each arm, each leg being engageable with one of said straps when the straps are moved toward the arms to force the arms away Ifrom said main shaft thereby unlocking said'ram for retraction.

7. The jack mechanism as claimed in claim 6 including spring biasing means operatively connected to said ram and shell for automatically retracting said ram when said teeth engaging surfaces are out of engagement with said teeth.

8. A hydraulic jack mechanism comprising an outer shell, an extensible, hollow ram telescopically mounted in -one end =of said shell, a ram base closing off one end of said ram, a fluid reservoir in said shell, fluid connecting means between said reservoir and the inner face of said ram base, a fluid pressurizing means in said fluid connecting means for drawing fluid from said reservoir and forcing it against the ram lbase thereby extending said ram, internal locking means within said reservoir for locking said ram in an ex ended position, said internal locking means including two components relatively movable along longitudinal axis of said shell, first means connecting a first one of said components to said ram, second means connecting a second one of said components to said shell, rneans for moving said components into cooperative yengagement to lock said ram in a fixed position relative to the shell, a release slidably mounted through one end of said shell and extending into said fluid reservoir, strap means hanging from said lock release, a diagonal cam slot in said strap means, pin means fastened to said second means and extending through said cam slot whereby vertical movement of said lock release will cause said strap means to move toward and away from said first `one `of said components, a laterally extending leg on said first one of said components, said leg being engageable with said strap means upon movement of said strap means toward the first one of said components to force the first one of said components away from said second means thereby unlocking said ram to permit said ram to be moved relative to the shell, and spring means connected to said ram for automatically retracting the ram when the components have been moved out of cooperative engagement.

9. A hydraulic jack mechanism comprising an outer shell, an extensible hollow ram reciprocally telescoped in one end of said shell, said ram being closed at one end by a ram base, a hollow shaft mounted in said r-am, an annular shaft head :fastened to the shaft and to the shell at the other end of the shell, a shaft base on said shaft, said outer shell, shaft head, and shaft base defining a fluid reservoir, said shaft base being slidably received against the inner wall surface of said ram, a fluid passageway through said shaft base, a cylinder within said main shaft, a piston reciprocally mounted in said cylinder, the top of said piston extending through the center of said shaft head, a pum-p handle on the top of the piston, a fluid feeding chamber in the bottom of said piston, an open fluid path between said feeding chamber and reservoir, an outlet from said feeding chamber, a first one-way check valve in said outlet, said first check valve permitting fluid to flow through said feeding chamber and flood said cylinder during the upstroke `of the piston, a fluid outlet from said cylinder communicating with said fluid passageway of the shaft base, a second one-way check valve in sa'd fluid outlet from said cylinder, said second check valve permitting fluid to be expressed from said cylinder during the downstroke of said piston to force said ram base away from said shaft base, and thereby extend said ram, a fluid byapass around said check valves whereby fluid can be expressed from `between said shaft base and ram base into said reservoir so that said ram can be retracted, internal locking means within said reservoir for locking said ram in an extended position, said internal locking means including teeth formed on the peripheral surface of said main shaft, a pair of arms pivotally mounted on said rain, said arms having teeth engaging surfaces located on opposite sides of said shaft, spring means surrounding said arms whereby said teeth engaging surfaces are yieldably urged into co-operative engagement with said teeth, a lock release sldably mounted on said main shaft, a pair of straps hanging from said lock release adjacent opposite sides of said main shaft, a diagonal cam slot in each strap, the cam slot in one stnap being formed crosswise of the cam slot in the other strap, a pair of pins fastened to the main shaft and extending through said cam slots whereby vertical movement of said lock release lwill cause said straps to move toward and away from said arms, a laterally extending leg on each arm, each leg being engageable with one of said straps when the straps are moved toward the arms to force the arms away from said main shaft thereby unlocking said ram for retraction, and spring means connected to said ram for automatically retracting the ram when the Iteeth engaging surfaces of said ram are out of contact with said teeth.

l0. A jacket mechanism comprising an outer shell, an extensible hollow ram concentrically mounted within said shell, a main shaft mounted within said ram, said main shaft being fixedly secured to said shell, pressure means for extending said ram, internal locking means for locking said ram in an extended position, said internal locking means including teeth formed on the peripheral surface of said main shaft, an arm at opposite sides of said shaft, spring means surrounding said arms to an annular shaft head shell at the other end of the shell, a shaft base on said shaft, said outer shell, shaft head and .shaft base dening a Enid reservoir, said 'shaft ibase 'being slidably received against the inner wall surface of ysaid ram, a fluid passageway through said shaft ibase, a cylinder Within said main shaft, a piston reciprocally mounted in said cylinder, the top .of said piston extending through the center of said passageway of the shaft valve in said iiud outlet ibase, ia second one-way check from said cylinder, said second check valve permitting -iluid to be expressed from said cylinder during the do'wnstroke of said piston to force said ram ibase laway from said yshaft main shaft, a [pair rof arms pivotally mounted on said ram shaft, a pair of straps connected to lsaid llock release, said straps being positioned on opposite sides of said 'main shaft, a diagonal cam slot in each strap, the cam slot in one strap being formed crosswise of the cam slot in the other strap, a pin fastened to each of said opposite sides of the main shaft and extending into thekcam slot formed in the adjacent strap whereby vertical movement of said lock rele-ase will cause said straps to move toward and away from saidA arms, *a laterally extending leg on each arm, each leg bei-ng engagealble ywith #one of said straps during lateral References lCited in the file'o'f this patent UNITED STATES PATENTS 697,449 Collins Apr. 15, 1902 1,248,861 Holloway Dec. 4, 1917 1,496,418 Kahn June 3, 1924 2,146,403 Nilsen Feb. 7, 1939 2,434,949n Mueller Jan. 27, 1948 2,624,174 Loef Ian. 6, 1953 2,700,436 Bernaerts Jan. 25, 1955 

1. A JACK MECHANISM COMPRISING AN OUTER SHELL, A HOLLOW, EXTENSIBLE RAM TELESCOPICALLY MOUNTED IN ONE END OF SAID SHELL, SAID SHELL AND SAID RAM DEFINING A SUBSTANTIALLY CLOSED FLUID RESERVOIR, MEANS DEFINING A PRESSURE CHAMBER WITHIN SAID HOLLOW RAM FOR HYDRAULICALLY MOVING SAID RAM, AND A RATCHET-TYPE INTERNAL LOCKING MEANS WITHIN SAID RESERVOIR FOR LOCKING SAID RAM IN AN EXTENDED POSITION, SAID INTERNAL LOCKING MEANS INCLUDING TWO COMPONENTS RELATIVELY MOVABLE ALONG THE LONGITUDINAL AXIS OF SAID SHELL, FIRST MEANS CONNECTING A FIRST ONE OF SAID COMPONENTS TO SAID RAM, SECOND MEANS CONNECTING A SECOND ONE OF SAID COMPONENTS TO SAID SHELL, MEANS FOR MOVING SAID COMPONENTS INTO CO-OPERATIVE ENGAGEMENT TO LOCK SAID RAM IN A FIXED POSITION RELATIVE TO THE SHELL, A LOCK RELEASE SLIDABLY MOUNTED THROUGH ONE END OF SAID SHELL AND EXTENDING INTO SAID FLUID RESERVOIR, STRAP MEANS HANGING FROM SAID LOCK RELEASE, A DIAGONAL CAM SLOT IN SAID STRAP MEANS, PIN MEANS FASTENED TO SAID SECOND MEANS AND EXTENDING THROUGH SAID CAM SLOT WHEREBY VERTICAL MOVEMENT OF SAID LOCK RELEASE WILL CAUSE SAID STRAP MEANS TO MOVE TOWARD AND AWAY FROM SAID FIRST ONE OF SAID COMPONENTS, A LATERALLY EXTENDING LEG ON SAID FIRST ONE OF SAID COMPONENTS, SAID LEG BEING ENGAGEABLE WITH SAID STRAP MEANS UPON MOVEMENT OF SAID STRAP MEANS TOWARD THE FIRST ONE OF SAID COMPONENTS TO FORCE THE FIRST ONE OF SAID COMPONENTS AWAY FROM SAID SECOND MEANS THEREBY UNLOCKING SAID RAM TO PERMIT SAID RAM TO BE MOVED RELATIVE TO THE SHELL. 